Interrupting device employing continuous hydraulic control



Sept. 24, 1963 H. L- PEEK ETAL 3,105,126

INTERRUPTINGDEVICE EMPLOYING CONTINUOUS HYDRAULIC CONTROL Filed June 15, 1960 2 Sheets-Sheet 1 INTERRUPTING DEVICE EMPLOYING CONTINUOUS HYDRAULIC CONTROL Filed June 15, 1960 2 Sheets-Sheet 2 United States 3,105,126 Patented Sept. 24, 1963 3,105,126 INTERRUPTING DEVICE EMPLOYING CON- TINUOUS HYDRAULIC CONTROL Henry L. Peek, Wellesley, Mass, and Julius W. Timmerman, Huntington, N.Y., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Filed June 15, 1960, Ser. No. 36,261 11 Claims. (Cl. 200-82) This invention relates to circuit breaker operating systems and more particularly to high speed circuit breaker operating devices which use stored energy for closing pairs of arcing contacts.

The operation of a high capacity circuit breaker requires an energy storage device which will substantially instantaneously release a tremendous quantity of energy. The closing operation of a typical high capacity circuit breaker may demand as much as 130,000 inch pounds of efi'ort delivered during one-tenth of a second. This is approximately two hundred horsepower. It is not economical to provide a continuous source of power of such a value. Hence, energy storage at the location in the form of storage batteries, compressed air, or springs has been the conventional solution. These systems have all been handicapped by the means required to translate the stored energy into final mechanical motion, or by the complex methods of the original translation of energy to the bulky storage means. As circuit breakers are frequently required to operate in isolated locations, an operating mechanism which requires a minimum of maintenance is imperative.

The hydraulic operating mechanism described herein is'proved to meet all of the requirements of a circuit breaker prime mover. This particular arrangement of the hydraulic operating mechanism couples a pneumohydraulic system with a mechanical trip free operator. It should be understood, however, that other arrange ments can be made similarly adaptable to the nontrip free and electrically trip free types of operator Without departing from the spirit of this invention.

Hydraulic systems have certain characteristics which make them desirable as an operating medium. The incompressibility of liquids permits the instantaneous transmission of power between two points as with a mechanical linkage. Unlike the mechanical linkage, however, liquids can be transmitted through tubes in all directions without loss of function and without the use of bell cranks or other bulky or complicated apparatus. Bearings and guides are unnecessary. Transformation and translation of power can be easily and simply accomplished. Compactness is an inherent characteristic of modern high pressure hydraulic systems.

It has been noted, however, that conventional hydraulic valves of the spool type for this type of high pressure hydraulic use must be manufactured to close tolerances and finishes to avoid leaks or binding of the movable parts. Poppet type valves although not requiring close tolerances and only a good finish over a small part of the valve element to render it leak proof have been heretofore avoided because of the difliculty of opening the pressure sealed valve element.

In accordance with the invention claimed a new and improved circuit interrupting device is provided employing a new three-way pilot operated poppet valve and associatcd cylinder, piston arrangement. This circuit interrupting device comprises a pair of relatively movable contacts, a motor comprising a cylinder and differential piston for causing relative movement of the contacts, a source of fluid under pressure, a control valve and a pilot valve for causing actuation of the piston upon the flow of fluid under pressure therethrough, and means for simultaneously connecting the source to one end of the cylinder to apply pressure to one side of the piston and to the valves. The control valve is arranged to admit fluid under pressure from the source to the other end of the cylinder .to apply pressure to the other side of the piston. The pressure on said other side of the piston overcomes the pressure on said one side of the piston and actuates the piston in one direction. The fluid in said one end of the cylinder is then forced out of the cylinder against the pressure of the source and into a reservoir. The control valve is arranged to drain the fluid to the reservoir from said other end of the cylinder under pressure of the source on said one side of piston upon actuation of the piston in a second direction. The pilot valve is provided for controlling the actuation of the control valve to cause the control valve to initiate actuation of the piston in first one direction and then the other direction.

It is therefore, one object of the present invention to provide a new and improved control arrangement for con-trolling the opening and closing operations of the movable contacts of a circuit breaker structure.

Another object of this invention is to provide a new and improved circuit breaker operating system in which the function of admitting and exhausting fluid under pressure from a double acting contact actuating hydraulic cylinder are performed by a three-way valve.

A further object of this invention is to provide a new and improved circuit breaker operating system in which fluid pressure is constantly maintained in one end of a double acting contact actuating hydraulic motor while operation is elfected by the admittance to or exhausting of fluid under pressure from its other end.

A still further object of this invention is to provide a new and improved circuit breaker operating system in which the pilot valve can be removed from the assembly for maintenance purposes without disturbing any pressure connections to the control valve or hydraulic contact actuating motor.

A still further object of this invention is to provide a new and improved piston actuating system in which the piston is constantly under pressure.

A still further object of this invention is to provide a circuit breaker operating system in which the opening and reclosing speeds thereof are not affected by the ambient temperature, corrosive atmosphere in the immediate vicinity of the operator, or long periods of inactivity of the operator.

Other objects and advantages of this invention will be apparent from the following description when read in connection with the accompanying drawings, in which:

FIG. 1 represents, partly in section, a circuit breaker operating system in contact closed position with the piston of the hydraulic motor in its deenergized reset position and embodying the present invention; FIG. 2 is a partial view of the circuit breaker operating structure shown in FIG. 1 in the contact closed position with the piston of the hydraulic motor still energized at the end of its contact closing stroke; and

FIG. 3 is a cross sectional view of the valve stem shown in FIG. 2 taken along the line III-III.

Referring more particularly to the drawings by characters of reference, FIG. 1 illustrates a hydraulically operating trip free mechanism 11 [for a circuit breaker 12. The hydraulically operating trip free mechanism 11 comprises a hydraulic motor 13 of the cylinder and piston type and a trip free type linkage 14. Motor 13 and circuit breaker 12 are operatively connected by linkage 14.

As diagrammatically shown, the circuit breaker 12 comprises a pair of stationary contact members 15 and a movable contact member 16. The circuit breaker 12 is biased to open circuit position by means of accelerating spring 17. The movable contact member 16 is supported by a breaker rod 18 which, in turn, is supported by lever 19 pivoted at 20. Lever 19 is connected to the. trip free oper-ating linkage 14 by means of operating rod 21.

The operating linkage 14 comprises a lever 22 pivoted f at 23 and a lever 2-4 pivoted at 25. Levers 22 and 24- are interconnected by a toggle comprising two toggle elements 26 and 27. Toggle element 26 is pivotally connected to lever 24 by a pin carrying a roller 28, land toggle element 27 is pivotally connected at 29 to lever 22. Toggle elements 26 and 27 are pivotally joined together by a pin 30. Pin 30'supports a roller 31 which is acted upon-by an operating ram 32.

- In the contact closed position of the operating linkage 14, the upper position of pin 39 and roller 31 is controlled by an abutment 36; This abutment is made of any suitable resilientmaterial and is adapted to minimize vibrations of the frame of the trip free mechanism "ill due to the impact of linkage 14 upon abutment 36. In the closed position of the circuit breaker 12, .pin 30 forming the joint or connection between toggle elements 26 and 27 is supported by a spring biased prop 33. Spring 34 resets linkage 14 upon a trip free operation. Spring 34 is secured at one end on the frame of the trip free operating mechanism 11 and. at the other end to pin 30 of toggle element 27.

' Circuit breaker 12 is tripped by spring 17 upon a predetermined movement of a tripping mechanism 46. Tripping mechanism 40 comprises a spring biased lever 41 pivoted at 42 and a trip solenoid 45 comprising a plunger 46-adapted to act on lever 41. Plunger 46 can be operated either electromagnetically by energizing solenoid 45 or mechanically by manual means, i.e., by hand operation of lever 41. Rotation of lever 41 about point 42 in the counterclockwise direction under the action of a force component transmitted to it by roller 28 causes counter- 7 clockwise movement of lever 24-fo-llowed by collapse of the toggle formed by toggle elements 26 and 27 and return of lever 24 to the position shown to cause the separation of the circuit breaker contacts 15, 16.

In order to close the circuit breaker 12, a suitable liquid under pressure such as oil is admitted to hydraulic motor 13 which comprises a cylinder 7, a piston 8 and ram 32 from a reservoir of stored energy. In this hydraulic 56 which seals oil opening 54 when the oil is completely alloy steel balls which in combination with the conical seats 70 land 71 are utilized to provide metal to metal poppet seating. These poppet seats are pressure sealed and self-cleaning. Valve elements 67 and 68 are actuated by a low power solenoid 72 having a very small time constant and controls the system pressure in such a manner as to control the actuation otthe control valve 64 without excessive delay. Control valve 64'comprises a valve stem or plunger 73 operating in housing 74 and a pair of ball type valve elements 75 and 76. Plunger 73 is provided to operate within housing 74 of valve 64 to actuate valve elements 75 and 76 sequentially off of their conical seats 77 and 78, respectively. As mentioned with regard to the pilot valve 63, valve elements 75, and 76 may be high carbon chrome alloy steel balls which in combination with their conical seats provide metal to metal poppet seating which are pressure seated and quirements of the circuit breaker, the pressure of the operating system and the pipe size of the system. The higher the system pressure, the greater the horsepower per cubicinch of liquid. It is desirable to use as high a pressure as practicable to keep thevolume of liquid to be moved to a minimum. The choice of pressures to be used is one of economy and reliability. A pressure of three thousand pounds per square inch was found. to be acceptable. The

V pipe size of the system was determined by the liquid volurne and velocity relationship required. All pipe lines are kept as short as possible and with smooth bends where needed. e The circuit breaker system in the drawing is shown wit the contacts 15 and 16 in the closed circuit position and the tripping mechanism in a corresponding position. Upon the energization of trip solenoid 45, plunger 46 actuates lever 41 counterclockwise about point 42. The

counterclockwise rotation of lever 41 releases or unlocks the tripping mechanism 14. Upon counterclockwise movementof lever 41, roller 28 moves upward under the action of spring 17' causing the collapse of the toggle l formed by elements Q6 and 2.7 and the separation of conexpelled from shell 51. This'action prevents the bladder 53 from extruding through the opening 54.

The accumulator bladder 53is precharged with dry nitrogen to approximately two-thirds of the desired system operating pressure. With no :oil in'the accumulator, the bladder fills the entire interior of the. accumulator shell 51. As oil is forced into the accumulator from a reservoir 60 by means of a hand or a motor driven pump 62, it compresses the bladder 53 and the pressure rises in accordance with BoylesLaW. The only permanent stress which the bladder encounters is compression of its wall Wh'iChlS equal to the systems or precharge pres-v "sure.

7 high speed solenoid actuated pilot valve 63 and a control valve 64. Pilot valve 63 comprises a springbiased valve 69 of valve 63 to actuate the valve elements sequentially oil of their conical valve seats and 71, respectively.

- The valve elements 66 and 67 may be high carbon chrome '70 stem 65, ball type valve elements 66'and 67. and a plunger 7 68;. Plunger 63 is provided to operate within thehousing shown in FlG. l.

tacts l5, 16. During the collapse of elements. 26, 27, pin 3%) slides on prop 33.

Upon the complete collapse of the toggle formed by elements 26, 2'7,-roller 25 settles back on its support 37,

and leverell rotates clockwise under its biasing means to its original position where it holds roller 28' against its support 37. V I p Before the operating mechanism may be electrically or manually operated for high speed closing of the circuit breaker contacts 15 and 16, the oil pressure accumulator 56 should be at normal operating pressure and the manual operating lever 86 for solenoid operating. pilot valve 63 should be in the position shown in FIG. 1. Oil pressure then builds upin pipe 81 above'piston 8 in cylinder 7 and in pipe 82 forcing valve element 67 of pilot'valve 63 against its valvesea-t 71. Asshown in FIG. 1, pipe 81 leads into and out ofa cavity 83 in housing 74 of control valve 64- and in cooperation with spring 79 forces valve element 'against its valve seat '77. With the oil pressure in accumulator Siland the associated pipe lines raised to ,its'operating' pressure, the system is then readyfor power operation to close the circuit breaker contacts 15 and 126 and return'thetrip free linkage 14 to the position The closing operation is triggered either electrically or mechanically. To electrically close the circuit breaker contacts, solenoid 72 is energized and because of the small time constant of the solenoid'quickly actuates valve elements 66 and 67 by raising armature 84 and plunger 65 of solenoid 72 to seat valve element 66 against its valve seat 70. Valve element 67 is simultaneously lifted from its valve seat 71 through the action of valve element 66 on push rod or plunger 68. Oil under full system pressure then flows through pipe line 86 through housing 69 of pilot valve 63 and into a cavity 87 of housing 74 and acts on a piston 88 of control valve 64. Oil under pressure in cavity 87 shifts piston 88 horizontally to the left as shown in FIG. 2 and in turn valve element 76 to its valve seat 78 causing plunger 73 simultaneously to unseat valve element 75 from its valve seat 77. This occurs even though oil under pressure exists in cavity 83 of housing 74- because of the larger pressure area of piston 88 exposed to the system pressure in cavity 87 compared to the area of valve element 75 exposed to the system pressure in cavity 83. Oil in pipe 81 is then provided a passageway from cavity 83 in housing 74 of control valve 64 through valve seat 77, around plunger 73 having a triangular cross section as shown in FIG. 3, through passage 89 in housing 74 and into the lower end of cylinder 7 of motor 13. Because of the much greater area on the lower side of piston 8, as compared to its upper side as shown in FIG. 1, piston 8 and ram 32 rises closing circuit breaker contacts 15, 16 and forcing the volume of oil above piston 8 back into accumulator 50.

The closing force of motor 13 is applied to linkage 14 by engagement of ram 32 with roller 31. Toggle elements 26 and 27 in moving upward during a closing stroke of piston 8, rotate lever 22 about its pivot point 23 in the clockwise direction. That rotary motion of lever 22 causes operating rod 21 to move downward. The downward movement of rod 21 causes lever 19 to rotate counterclockwise about its pin 20, thereby closing the breaker 12 against the action of accelerating spring 17.

When the toggle elements 26 and 27 reach prop 3,3 in their upward movement under the action of piston 8 and ram 32, pin 30 biases prop 33 clockwise and slides on it until roller 31 reaches abutment 36. After pin 30 slides on prop 33, prop 33 rot-ates counterclockwise under the action of its biasing means until it is in a position to support pin 30. Lover 41 retains roller 28 in position adjacent stop 37. The toggle formed by elements 26 and 27 is retained in contact closed position by the combined action of prop 33 andrlever 41.

A closing operation is completed when the circuit breaker contacts are closed and the prop 33 and lever 41 have locked the toggle elements in this contact closed position. When the circuit breaker contacts 15 and 16 have reached their contact closed position, solenoid 72 is deenergized by a limit switch (not shown). Fluid under pressure in pipe 82 then forces valve element 67 against its valve seat 71 and causes plunger 68 to unseat valve element 66 thereby exhausting oil under pressure to the right of piston 88 through passageway 86, valve seat 70 and pipe 90 into reservoir 60 causing oil under pressure in pipe 81 and cavity 83 of housing 74 of control valve 64 to again seat valve element 75 and unseat valve element 76 through the movement of plunger 73. When valve element 76 is unseated, the oil under pressure below piston 8 is exhausted to reservoir 60 through passageway 89 in housing 74 of control valve 64, valve seat 78, pipe 91 and pipe 90. This causes oil under pressure from the accumulator 50 always present in pipe 81 and above piston 8 of motor 13 to quickly return piston 8 to its lower most position as shown in the drawings which provides space for rapid recoupling of the associated trip free circuit breaker mechanism. Control valve 64 remains in the extreme right hand position and pilot valve remains in its lower position when solenoid 72 is deenergized. Reservoir 68 may be open to atmospheric pressure or closed and having an air cushion above the oil level, as desired. I

Energy expended during operation is replenished inthe accumulator by the power driven pump 62 or a hand pump 92. The maximum and minimum system pressures are controlled by a pressure actuated motor switch (not shown).

For manual full speed closing of the circuit breaker contacts 15, 16 with oil at normal operating pressures, the manual operating lever is rotated clockwise causing cam surface 93 to raise armature 84 of solenoid 72 mechanically thereby initiating a sequence of operation identical to the operation described wherein armature 84 is actuated under the influence of current flowing through the coil of solenoid 72. Upon release of manual operating lever 80, spring 94 fastened to handle 80 and the frame of the solenoid 72 will reset lever 80 and cam 93 to its normal position shown in FIG. 1 causing spring 95 mounted around armature 65 to return it to its normal position shown in FIG. 1.

The hand pump 92 may also be used as a maintenance closing device. To close the circuit breaker by hand with the accumulator, discharge lever 80 is rotated clockwise to unseat valve element 67 from valve seat 71. Oil under pressure then flows through the system in the same manner as heretofore explained except that the hydraulic mechanism then acts as a simple hydraulic jack and the circuit breaker can be jacked closed or to any intermediate position. Check valves within the hand pump lock the circuit breaker positively in any position, afford- 1 ing the maximum safety to inspection or maintenance personnel.

The hydraulic operating system offers several important advantages to the use-r of power circuit breakers. Maintenance is reduced to a minimum by virtue of the few moving parts which are employed. All moving parts within the system are constantly immersed in a liquid having excellent lubricating properties, therefore wear between sliding surfaces is minimized. The completely sealed system protects all internal surfaces from corrosive effects of moisture and dirt. The small physical size of the hydraulic operating mechanism and its light weight make it easy to handle.

The hydraulic operating mechanism provides high speeds of operation when needed. Reclosing speeds far in excess of those presently required by circuit breaker standards are easily attainable.

The high efiiciency of the hydraulic system has resulted in the reduction of the size of the motor required in the liquid supply unit. Compared to a pneumatic system of the same capacity, the motor required by the hydraulic system is much smaller. The pump up time from zero pressureto full operating pressure is about twenty-five percent of the time required on an air pressure system.

Tests indicated the ability of the hydraulic operating mechanism to obtain very high reclosing speeds. When coupled with a toggle linkage as shown, it is necessary that the ram 32 be rapidly retrieved from its upper position during repetitive reclosures of the breaker contacts. This is necessary to allow the mechanical trip free mechanism to reset quickly and permit the next reclosure. The return of ram 32 to its lower position was found to be controlled by the time necessary to shift valve elements 70, 71 and 72 of control valve 64 from left to right. It Was determined by experiment, that the valve speed is approximately proportional to the operating pressure of the hydraulic system. Oscillograms show that pressure is instantaneously applied to piston 8 of motor 13 to actuate ram 32 to its lower position immediately after valve stem 69 of valve 64 starts to move to the left. To fully utilize the high speed characteristics of the hydraulic system, it is necessary to secure high control valve speeds.

The new and improved three way valve disclosed and claimed herein in combination with the circuit breaker tripping mechanism seals against leaks by the fluid pressure itself and is accomplished without the necessity of close tolerances. By use of the pilot valve only a small amount of force is needed for control valve actuation. In both the contnolvalve and the pilot valve simple readily attainable steel balls are utilized for the movable poppet valves thereby simplifying replacement and maintenance. Pressure is constantly maintained at one end of the fluid motor 13 thereby eliminating the need for a valve at that end of the motor structure. Further, quick reversal action of piston8 of motor 13'is accomplished without the use of a return spring by the application of 'accumulator pressure at all times on the upper sideof the piston as shown in the drawings.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

Having now particularly described and ascertained the nature of our said invention and the manner in which it is to be performed, we declare that What we claim is:

l. A circuit interrupting device comprising a pair of relatively movable contacts, a motor comprising a cylinder and a differential piston for causing relative movement of said contacts, a source of fluid under pressure, a valve having a diflerential valve element, means for simultaneously connecting said source of fluid to one end of nd direction, said valveupon actuation thereof initiating actuation of said piston in a second direction, said valve and said piston being actuated against the bias of said source.

2. A circuit interrupting device comprising a pair of relatively movable contacts, a motor comprising a cylinder and a differential piston for causing relative movement of said contacts, a source of fluid under pressure, a control valve, a pilot valve, means for simultaneously connecting said source of fluid to oneend of said cylinj der and to each of said valves for biasing said piston and said valves in one direction, and means for actuating said pilot valve in a second direction-for causing actuation of said control valve in a second direction, said control valve upon actuation thereof initiating actuation of said piston in a second direction, said valves and said piston being actuated against the bias of said source.

3. Acircuit interrupting device comprising a pair of relatively movable contacts, a motor comprising a cylin der and a diiferential piston for causing relative move- 'ment of said contacts, one side of said piston having a sure fromsaid source to the other end of said cylinder to apply pressure to said otherside of said piston, said pressure on said other side of said piston overcoming the pressure on said one side of said piston to actuate said piston in one direction, said fluid in said oneend of said cylinder eing forced out of said cylinder against the pressure f said source. 1 t

4. A circuit interrupting device comprising a pair of relatively movable contacts, a motor comprising a cylinder and a differential piston for causing relative movement of said contacts, one side of said piston having a relatively smallpressure area and the other side of said it piston having a relatively large pressure area, a source of fluid under pressure, a control valve for causing actuation of said piston upon'the flow of 'fluid'under presside of said valve, said valve being arranged upon actuation thereof to admit fluid under pressure from said source to the other end of said cylinder to apply pressure to said other side of said piston, said pressure on said other side of said piston overcoming the pressure on said one sideof said piston to actuate said piston in one direction, said fluid in said one end of said cylinder being forced out of said cylinder against the pressure of said source, said valve being arranged to drain fluid from said other end of said cylinder to a reservoir under pressureof said source upon actuation of said piston in a second direction.

5. A circuit interrupting device comprising a pair of relatively movable contacts, a motor comprising a cylinder and a differential piston for causing relative movement of said contacts, a source of fluid under pressure, a control valve for causing actuation of said piston upon the flow of fluid under pressure therethrough, and means for simultaneously connecting said source of fluid to one end of said cylinder to apply, pressure to one side of said piston and to one side of said valve, said valve being arranged to admit fluid under pressure from said source to the other end of said cylinder to apply pressure to the other side of said'piston, said pressure on said other side of said piston overcoming the pressure on said one side of said piston to actuate said piston in one direction, said fluid in said one end of said cylinder being forced out of said cylinder against the pressure of said source, said valve being arranged to drain fluid from said other end of said cylinder to a reservoir, said valve upon draining fluid from said other end of said cylinder causing fluid under pressure of said source to actuate said piston in a second direction.

,6. A circuit interrupting device comprising a pair of relatively movable contacts, a motor comprising a cylinder and a differential piston for causing relative movement of said contacts, a source of fluid under pressure, a control valve and a pilot valve for causing actuation of said piston 1 upon the flow of fluid under pressure therethrough, and

means for simultaneously connecting said source to one end of said cylinder to apply pressure to one side of said piston and to one side of each of said valves, said control valve'arranged to admit fluid under pressure from said 7 source to the other end of said cylinder to apply pressure to the other side of said piston, said pressure on said other side of said piston overcoming the pressure on said one side of said piston and actuating said piston in one direction, said fluid in said one end of said cylinder being forced out ofsaid cylinder against the pressure of said source, said control valve being arranged to drain fluid from'said other end of saidjcylinder under pressure of said source on said one side of said piston upon actuation of said piston in a second direction, said pilot valve controlling actuation of said control valve to cause said ranged upon actuation thereof to admit fluid under prescontrol valve to initiate actuation of said piston in first said one direction and then in said second direction.

7. A circuit interrupting device comprising a pair of relatively movable contacts, a motor comprising a cylinder and a differential piston for causing relative movee nt of said contacts, a pneumo -hydraulic' accumulator for supplying liquid under pressure, a control'valve and a pilot valve for causing actuation of said piston uponthe flow of liquid under pressure therethrough, and means for 7 simultaneously connecting said accumulator to one end of arranged to admit liquid under pressure from said source sure therethrough, and means for simultaneously connecting said source of fluid to one end of said cylinder to 7 apply pressure to said one side of said piston and to one said cylinder to apply pressure to one side of said piston and to one side of each of said valves, said control valve to the other end of said cylinder to apply pressure to the other side of saidpiston, said pressure on said other side of said pistoriovercoming the pressure on said one side of said piston andiactuating said piston in one direction, said liquidin. said one end oft said cylinder beingforced out {of saidcylinder' against the pressure of said accumulator and into said accumulator, said control valve being arranged to drain liquid to said reservoir from I said other end of said cylinder under pressure of said accumulator on said one side of said piston upon actuation of said piston in a second direction, said pilot valve controlling actuation of said control ,valve to cause said control valve to initiate actuation of said piston in first said one direction and then in said second direction.

7 8. A circuit interrupting device comprising a pair of relatively movable contacts, a motor comprising a cylinder and a differential piston for causing relative movement of said contacts, a pneumo-hydraulic accumulator for supplying liquid under pressure, a control valve and a pilot valve for causing actuation of said piston upon the flow of liquid under pressure therethrough, and means for simultaneously connecting said accumulator to one end of said cylinder to apply pressure to one side of said piston and toone side of each of said valves, said means holding said valves in one of their external positions, said control valve upon the application of liquid under pressure to the other side thereof admitting liquid under pressure from said accumulator to the other end of said cylinder to apply pressure to the other side of said piston, said pressure on said other side of said piston overcoming the pressure on said one side of said piston and actuating said piston in one direction, said liquid in said one end of said cylinder being forced out of said cylinder against the pressure of said accumulator, said control valve being arranged upon the reduction of liquid under pressure to said other side thereof to drain liquid from said other end of said cylinder, said piston being actuated in a second direction under pressure of said accumulator on said one side of said, piston upon liquid being drained from other end of said cylinder, said pilot valve upon actuation thereof control ling actuation of said control valve to cause said control valve to initiate actuation of said piston.

9. A circuit interrupting device comprising a pair of relatively movable contacts, a motor operable by liquid under pressure and comprising a cylinder and a pistonmovably arranged therein for causing relative movement of said contacts, acollapsible linkage of the trip free type for operatively relating the breaker to said motor, tripping means for causing collapse of said linkage to cause opening of said contacts, a ram on said piston separate from said linkage and cooperating therewith upon collapse thereof for re'closing said contacts, a control valve and a pilot valve for controlling the supply of liquid under pressure to said cylinder to cause actuation of said piston to reclose said contacts, and a source of liquid under pressure, said piston and said valves each being simultaneously biased by said source in given directions, and means for actuating said pilot valve for causing actuating of said control valve by said source, said control valve causing actuation of said 1Q piston in another direction, said valves and said piston being actuated in said other direction against the bias of said source.

10. A circuit interrupting device comprising a pair of relatively movable contacts, a motor operable by liquid under pressure and comprising a cylinder and a piston movably arranged therein for causing relative movement of said contacts, a collapsible linkage of the trip free type for operatively relating the breaker to said motor, tripping means for causing collapse of said linkage to cause opening of said contacts, a ram on said piston separate from said linkage and cooperating therewith upon collapse thereof for reclosing said contacts, a control valve and a pilot valve for controlling the supply of liquid under pressure to said cylinder to cause actuation of said piston to reclose said contacts, and a source of liquid under pressure, said piston and said valves being continuously biased by said source in a first direction, and means for actuating said pilot valve for causing actuating of said control valve by said source, said control valve causing actuation of said piston in a second direction, said valves and said piston being actuated against the bias of said source.

11. A circuit interrupting device comprising a pair of relatively movable contacts, a motor operable by liquid under pressure and comprising a cylinder and a differential piston movably arraanged therein for causing relative movement of said contacts, a collapsible linkage of the trip free type for operatively relating the breaker to said motor, tripping means for causing collapse of said linkage to cause opening of said contacts, a ram on said piston separate from said linkage and cooperating therewith upon collapse thereof for reclosing said contacts, a control valve and a pilot valve for controlling the supply of liquid under pressure to said cylinder to cause actuation of said piston to reclose said contacts, and a pneumo-hydraulic accumulator for supplying liquid under pressure, said piston and said valves being continuously biased by said source in a first direction, and means for actuating said pilot valve in a second direction for causing actuating of said control valve in a second direction, said control valve upon actuation thereof in said second direction causing liquid from said source to be applied to said piston to actuate it in a second direction, said valves and said piston being actuated in said second directions against the bias of said source.

References Cited in the file of this patent UNITED STATES PATENTS 2,658,969 Umphrey Nov. 10, 1953 2,730,589 Perry et "a1. Jan. 10, 1956 2,765,378 Perry et al Oct. 2, 1956 2,770,222 Anderson Nov. 13, 1956 

1. A CIRCUIT INTERRUPTING DEVICE COMPRISING A PAIR OF RELATIVELY MOVABLE CONTACTS, A MOTOR COMPRISING A CYLINDER AND A DIFFERENTIAL PISTON FOR CAUSING RELATIVE MOVEMENT OF SAID CONTACTS, A SOURCE OF FLUID UNDER PRESSURE, A VALVE HAVING A DIFFERENTIAL VALVE ELEMENT, MEANS FOR SIMULTANEOUSLY CONNECTING SAID SOURCE OF FLUID TO ONE END OF SAID CYLINDER AND TO ONE SIDE OF SAID VALVE ELEMENT FOR BIASING SAID PISTON AND SAID VALVE ELEMENT IN ONE DIRECTION, AND MEANS FOR ACTUATING SAID VALVE ELEMENT IN A SECOND DIRECTION, SAID VALVE UPON ACTUATION THEREOF INITIATING ACTUATION OF SAID PISTON IN A SECOND DIRECTION, SAID VALVE AND SAID PISTON BEING ACTUATED AGAINST THE BIAS OF SAID SOURCE. 